AN ABSTRACT OF THE THESIS OF

STEVEN D. LUKEFAHR for the degree of MASTER OF SCIENCE in

ANIMAL SCIENCE presented on September 29, 1980

TITLE: THE INHERITANCE OF SPERMATOZOAN MIDPIECE LENGTH AND ITS

RELATIONSHIP WITH TRAITS OF ECONOMIC IMPORTANCE IN CATTLE

Abstract approved: Redacted for Privacy

William D. Hohenboken

In two cattle populations; dairy and beef, the relationship

between a bull's average spermatozoan midpiece length and production

traits of economic importance was studied. In the first population

involving 39 Holstein sires, variation in midpiece length between

bulls and between ampules of semen from the same bull collected at

least six months apart was highly significant (P < .01). Differences

in midpiece length between ampules of semen prepared from the same

ejaculate were negligible. From two methods of computation, herit-

ability of midpiece length was estimated to equal (1.09 ± 1.03 and

1.30 ± 1.13. Phenotypic correlations between sire midpiece length

and daughter's average dairy production traits were low to moderate

but were consistantly negative. Phenotypic correlations between sire

midpiece length and his own merit for semen quality and fertility

traits were close to zero. This study suggested that midpiece length

might be heritable and might be correlated with economically impor-

tant production traits in dairy cattle.

In the second population involving 80 yearling Hereford bulls

(17 Polled Hereford and 63 Horned Hereford), variation within bulls

for midpiece length was small (average coefficient of variation = 2.5%).

Age did not significantly affect a bull's average midpiece length but

the breed difference was highly significant (P < .005) with Polled

Hereford bulls exceeding Horned Hereford bulls. Heritability of

midpiece length estimated from paternal half-sib analysis of variance

was 0.84 ± 0.56. Other estimates of heritability were computed for

reproductive and growth traits and were found to be higher than values

reported in the literature, perhaps due to a ranch of origin and/or

pen effects. In general, phenotypic correlation between bull average

midpiece length and his own reproductive and growth traits were low.

Genetic correlations between average midpiece length and growth and

reproductive traits were zero to moderate, and all were accompanied by

large standard errors. This study suggested that midpiece length in

Hereford cattle is highly heritable although further research is

needed involving more suitable beef cattle populations to determine

if midpiece length is correlated genetically with traits of economic

importance.

THE INHERITANCE OF SPERMATOZOAN MIDPIECE LENGTH AND ITS

RELATIONSHIP WITH TRAITS OF ECONOMIC IMPORTANCE IN CATTLE

by

STEVEN D. LUKEFAHR

A THESIS

Submitted to

Oregon State University

in partial fulfillment of

the requirements for the

degree of

MASTER OF SCIENCE

June 1981

APPROVED:

Redacted for PrivacyAssociate Professor of Animal Science

in charge of major

Redacted for Privacy

Head d%Animal Science

Redacted for Privacy

Dean of draduate School

Date thesis is presented September 29, 1980

Thesis typed by Mary Ann Airth for STEVEN D. LUKEFAHR

ACKNOWLEDGEMENTS

To the Animal Science team of researchers at the San Juan Basin

Research Center, Hesperus, Colorado of Colorado State University, the

author of this manuscript expresses his gratitude for the hospitality

and cooperation received during the trip involving semen collection

of beef bulls.

I wish to thank committee members, Drs. Ken Rowe and Art Wu,

for their assistance and/or advisement on my thesis. A word of

thanks is also expressed to the American Breeders Service, DeForest,

Wisconsin and to Dr. F. E. Elliott for the generous donation of bull

semen and provision of fertility records.

A special thanks is given to my major professor, Dr. William

Hohenboken, whose enlightening training and spirit has been most

inspiring to me towards development of a young scientist.

TABLE OF CONTENTS

Page

Introduction 1

Review of Literature 2

Spermatogenesis and Spermiogenesis 2

The Role of the Mitochondria 3

The Relationship between Midpiece Length andQuantitative Traits 7

Literature Cited 9

Technical Paper No. 5569: Characteristics ofSpermatozoan Midpiece Length and itsRelationship with Economically ImportantTraits in Cattle 12

Abstract 13Introduction 14Experimental Procedure 15

Results and Discussion 18

Acknowledgement 21References 22

The Inheritance of Spermatozoan Midpiece Length and itsRelationship with Growth and Reproductive Traits inHereford Cattle 30

Summary 30Introduction 30Materials and Methods 32Results and Discussion 35Literature Cited 38

Appendix 1. 42

LIST OF FIGURES

Figure Page

1 Spermatogenesis 4

2 Spermiogenesis 5

LIST OF TABLES

Table Page

Technical Paper No. 5569

1 Statistical properties of midpiece length basedupon the first of three measurements per cell 24

2 Hierarchical analysis of variance for differencesamong bulls and between ampules for midpiecelength 25

3 Hierarchical analysis of variance for differencesamong bulls and between collections for midpiecelength 26

4 . The association between genetic relationship andMPL difference for all possible pairs of bulls 27

5 Product-moment correlations between sire midpiecelength and daughters' dairy traits 28

6 Product-moment correlations between sire midpiecelength and semen quality and fertility traits 29

The Inheritance of Spermatozoan Midpiece Length and itsRelationship with Growth and Reproductive Triats inHereford Cattle

1 Least-Squares means, residual standard deviations,effects of age, breed and sires within breeds andheritabilities of average MPL and growth andreproductive traits 40

2 Phenotypic and genetic correlations betweenaverage MPL and growth and reproductive traits 41

APPENDIX

Appendix

Technical Paper No. 5569

1 Average MPL, variance of MPL, percent repeatabilityand predicted differences for several milk produc-tion traits for each of 39 Holstein bulls.

Page

42

THE INHERITANCE OF SPERMATOZOAN MIDPIECE LENGTH AND ITS

RELATIONSHIP WITH TRAITS OF ECONOMICS IMPORTANCE IN CATTLE

INTRODUCTION

In animal breeding, an economical trait of interest can be altered

genetically through direct, indirect or index selection. When an

animal is selected on the basis of its own phenotypic merit for the

trait of interest, direct selection has been practiced. In urilizing

single trait direct selection, the heritability of the trait is the

only genetic information of interest. Alternatively, a trait can be

altered through selection emphasis on a second trait, i.e., indirect

selection. This is possible when the second trait is heritable and is

genetically correlated with the economic trait of interest. With

indirect selection, the heritability of both traits as well as the

genetic correlation between them is needed to predict selection

response. Assuming that the traits are genetically correlated, the

economic trait of interest can be improved at a more rapid rate when a

combination of both direct and indirect selection is practiced. For

index selection combining information from both traits, the herit-

abilities of both traits and the genetic and phenotypic correlations

between them are needed.

In mice, Beatty (1969) found a positive relationship between

spermatozoan midpiece length (MPL) and body weight at maturity. Among

four divergent lines, a 0.2 um increase in MPL was associated with a

10 gram increase in body weight. Beatty hypothesized that an increase

in mitochondrial content (synonymous with an increase in MPL) might

cause a higher rate of oxidative phosphorylation which could affect the

2

manifestation of a wide array of energy dependent characters (e.g.,

body weight). Estimates of heritability for MPL in mice are high;

0.76 ± .02 (Woolley, 1970b) and 0.97± .36 (Woolley and Beatty, 1967).

Primarily because of the above mouse experiments, this work was

initiated. In two cattle populations, dairy and beef, the biologi-

cal relationship with certain economic traits and the heritability

of spermatozoan midpiece length will be investigated and reported.

REVIEW OF LITERATURE

Spermatogenesis and Spermiogenesis

Spermatogenesis is the process by which sperm cells develop in

the testes of the male. In meiosis I of spermatogenesis, a primary

spermatocyte divides by meiosis to form two secondary spermatocytes.

The significance of this process is the reduction of chromosomal

material from the diploid to the haploid number (in cattle 2n = 60 -0 n

= 30). In meiosis II, each secondary spermatocyte divides mitotically

to produce two nonmotile spermatids (see Figure 1). During spermio-

genesis, the metamorphosis of each nonmotile spermatid into a viable

spermatozoan requires approximately fifteen days (Hafez, 1975, p. 101-

122). Migration of centrioles, Golgi apparatus, mitrochondria and

other cytoplasmic entities to specific regions on the spermatid also

takes place during spermiogenesis (see Figure 2).

Migration of mitochondria in the cytoplasm of the spermatid to

the proximal region of the flagellum (tail of the sperm cell) occurs

during spermiogenesis. The quantity of mitochondria found in this

3

region is determined by the deposition of a fibrous periflagellar

sheath on the main-piece of the early spermatid (Yasuzumi, 1956:

Sotelo and Trujillo-Cenoz, 1958). There is some evidence that there

are more mitochondria found in the cytoplasm of the spermatid than

are incorporated in the midpiece (Bishop and Walton, 1960). Migrat-

ing to opposite ends of the midpiece are the proximal and distal

centrioles (Lommen, 1967). It is after deposition of the periflagel-

lar sheath and the migration of the centrioles that mitochondria

conjugate on the midpiece.

After a brief period of turgidity and contortion, mitochondrial

units align themselves and transform to an a-helical configuration,

resembling the structure of the DNA molecule (Woolley, 1970). Woolley

(1970) also reported that differences between individual sperm cells

in MPL were associated with differences in the number of spiral

units or gyres. Furthermore, it was calculated that each mitochon-

drion occupied 0.58 of one gyre. Thus, differences in MPL between

cells are attributable to differences in mitochondrial content.

Significant variation in MPL among males has been well documented in

mice (Woolley 1970; Beatty, 1970, 1971; Sharma, 1960). On the

spermatozoan midpiece of bull, man and mouse, approximately 10, 10

and 350 mitochondria are found (Fawcette, 1975).

The Role of the Mitochondria

The mitochondrion is the primary site of energy transformation in

all eukaryotic organisms. The enzymatic systems controlling the

MITOSIS

MEIOSIS I

MEIOSIS IL

I

GENESIS

.11

SPERNI10-

FIGURE 1. Spermatogenesis .

Spermatogonia

Primary Spermatocyte

Secondary Spermatocyte

Spermatids

Spermatozoa

EARLYACROSOMA L

CAP

%2UL..t.11 Ail'ARATUS

NUCLEUS

CYTOPLASM

MITOCHONDRIA

A CROSOME

CENTRIOLE RING

TAIL

'PROXIMAL CENTR I OLE

DISTALCENTRIOLE

(JENSEN'S RING)

NUCLEUS TAIL DEVELOPING

ACROSOMALCAP

HEAD

MITOCHONDRIA

CYTOPLASM CAST OFF

DISTALMIDPIECE ,CENTRIOLE

NAILCYTOPLASMIC DROPLET

PROXIMAL CENTRIOLE

FIGURE 2. Spermiogenesis (Adaptation of Hafez, 1975).

6

Krebs Cycle, oxidative phosphorylation and the electron transport

chain all occur in the inner membrane of the mitochondrion matrix

(Lehninger, 1973, p. 509-542). It has been established that the

mitochondria possess their own DNA and RAN (Wagoner, 1972), the DNA

strands existing in closed circles measuring about 5 pm in length

(Borst, 1970). Furthermore, nuclear and mitochondrial DNA coded

proteins may interact during cellular metabolism (Woodward, et al.,

1970). More specifically, cytochrome oxidase, a dimeric enzyme found

in the mitochondrion and active in electron transport, has subunits

whose amino acid sequences are coded by mitochondrial and nuclear

genes (Chen and Charalampous, 1969).

Bi-parental contribution of mitochondria to the zygote at ferti-

lization may occur. Under electron microscopy, Soupart and Strong

(1974) and Zamboni, et al. (1972) observed in human oocytes that

maternally and paternally derived mitochondria were present at

fertilization. On the contrary, Yasuzumi (1956) observed that in the

oocyte of the rat, degeneration of paternally derived mitochondria

(on the spermatozoan midpiece) took place within a matter of hours

of fertilization.

Polymorphism at mitochondrial loci has been hypothesized as an

underlying cause of differential respiration rates between lines of

mice (Wagoner, 1972), maize (Sarkissian and Srivastava, 1967) and

Drosophila (McDaniel and Grimwood, 1971). The interaction between

isolated mitochondria from parental types or strains in rate of

respiration has been used as a test for predicted parental combining

7

ability and actual heterois (McDaniel and Sarkissian, 1966; McDaniel

and Grimwood, 1971; Sarkissian and Srivastava, 1967). Lints and

Lints (1967, 1968, 1969), however, were unable to detect a strong

correlation between respiration rate and metric characters in

Drosophila.

The Relationship between Midpiece Length and Quantitative Traits

In mice, Beatty (1969) reported the existence of a positive

phenotypic relationship between spermatozoan midpiece length and

mature body weight. He found that for every 0.2 pm increase in MPL

an increase of 10 grams in body weight was observed. Beatty advanced

the hypothesis that an increase in MPL associated with mitochondrial

content was related to a higher rate of oxidative phosphorylation

and/or ATP synthesis. If this is true, it would be expected that a

great number of other traits would also be affected.

High estimates of heritability for MPL in mice (0.97 ± .36,

Woolley, 1970b) have been reported. Woolley (1970b) practiced bi-

directional selection for MPL in mice and demonstrated a rapid rate

of response for the trait. After thirteen generations of selection,

the lines differed in MPL by 5.4 phenotypic standard deviations, and

the responses were essentially symmetrical. One criticism of this

experiment could be that no attempt was made to investigate the re-

lationship between the change in mitochondrial content (midpiece

length) and other quantitative, energy dependent characters. The

relationship between MPL and fertility traits in mice was, however,

8

examined by Woolley (1970a). In that experiment, color coded males

representing three MPL lines; high, unselected and low, contributed

seminal collections. Samples were pooled, and heterospermic insemi-

nations to an unrelated line of inbred females were made. Results

showed no indication of differential fertilizing ability of sperma-

tozoa between the three paternal lines. After the birth of over 500

offspring, the hypothesis that a relationship existed between MPL

and fertility was rejected. Furthermore, Beatty and Mukherjee (1963)

and Pant (1971) have reported that neither age in males nor maternal

effects attributable to dams influenced MPL in mice.

In cattle, significant variation among breeds and among bulls

within breeds in spermatozoan MPL has been reported (Mukherjee and

Singh, 1965, 1966). Variation in MPL between seasons and/or collec-

tions and between slides within collections apparently are minimal

(Mukherjee and Singh, 1965, 1966). No attempt was made by these

workers to investigate the relationship between MPL and economically

important production traits.

Beatty, R. A. 1969.

mice selected for

Beatty, R. A. 1970.

Rev. 45:73-120.

Beatty, R. A. 1971.

organelles. In:

Spermatozoan

9

LITERATURE CITED

A genetic study of spermatozoan dimensions inbody weight. Indian J. Hered. 1:1-13.

The genetics of the mammalian gamete. Biol.

The genetics of size and shape of spermatozoanProc. Int. Symp. on The Genetics of the

97-115). Edinburgh.

Beatty, R. A. and D. P. Mukherjee. 1963. Spermatozoan characteris-

tics in mice of different ages. J. Reprod. Fertil. 6:261-268.

Bishop, M. W. H. and A. Walton. 1960. Spermatogenesis and thestructure of mammalian spermatozoa. In: Marshall's Physiologyof Reproduction (p. 1-101).

Borst, P. 1970. Mitochondrial DNA: structure, information content,replication and transcription. Symposia of Soc. Exp. Biology24:201-225.

Chen, W. L. and F. C. Charalampous. 1969. Mechanism of induction ofcytochrome oxidase in yeast. J. Biol. Chem. 244:2767-2776.

Fawcette, D. W. 1975. The mammalian spermatozoan. Develop. Biol.

44:394-436.

Hafez, E. S. E. 1975. Reproduction in Farm Animals, Third Edition.Lea & Febiger, Philadelphia.

Lehninger, A. L. 1977. Biochemistry, Second Edition. Worth Pub-lishers, Inc., New York.

Lommen, M. A. J. 1967. Development of the ring centriole duringspermiogenesis of the salamander, Desmognathus fuscus. J. Cell.

Biol. 35:82A-83A.

Lints, F. A. and C. V. Lints. 1967. Consumption of oxygen by the

egg of Drosophila melanogaster. Nature, Lond. 214:785-787.

Lints, F. A. and C. V. Lints. 1968. Respiration in drosophila - II.Respiration in relation to age by wild, inbred and hybrid

Drosophila melanogaster imagos. Exp. Geront. 3:341-349.

Lints, F. A. and C. V. Lints. 1969. Respiration in drosophila - III.Influence of preimaginal environment on respiration and aging inDrosophila melanogaster hybrids. Exp. Geront. 4:81-94.

10

McDaniel, R. G. and B. G. Grimwood. 1971. Hybrid vigor in droso-phila: Respiration and mitochondrial energy conservation.Comp. Biochem. Physiol. 38 B:309 -314.

McDaniel, R. G. and I. V. Sarkissian. 1966. Heterosis: Comple-mentation by mitrochondria. Science 152:1640-1642.

Mukherjee, D. P. and S.characteristics of213-220.

Mukherjee, D. P. and S.characteristics of104-108.

P. Singh. 1965. Breed differences inbull spermatozoa. Indian J. Vet. Sci. 35:

P. Singh. 1966. Seasonal variations in thebull spermatozoa. Indian J. Vet. Sci. 36:

Pant, K. P. 1971. Patterns of inheritance in the midpiece lengthof mouse spermatozoa. In: Proc. Int. Symp. on The Genetics ofthe Spermatozoon (p. 116-120). Edinburgh.

Sarkissian, I. V. and H. K. Srivastava. 1967. Mitochondrial poly-morphism in maize. II. Further evidence of correlation ofmitochondrial complementation and heterosis. Genetics 57: 843-850.

Sharma, K. N. 1960. Genetics of gametes. IV. The phenotype ofmouse spermatozoa in four inbred strains and their F1 crosses.In: Proc. Royal Soc. Edinburgh. 68:54-71.

Sotelo, J. R. and 0. Trujillo-Cenoz. 1958. Electron microscope studyof the kinetic apparatus in animal sperm cells. Z. Zellforsch.mikrosk. Anat. 48:565-601.

Wagoner, R. P. 1972. The role of maternal effects in animal breed-ing. II. Mitochondria and animal inheritance. J. Anim. Sci.35: 1280-1287.

Woodward, D. 0., D. L. Edwards and R. B. Flavell. 1970. Nucleo-cytoplasmic interaction in the control of mitochondrial structureand function in neurospora. Symp. Soc. Exptl. Biol. 24:55-69.

Woolley, D. M.quantity ofRes., Camb.

Woolley, C. M.midpiece in

1970a. A test of the functional significance of themitochondria in the spermatozoa of mice. Genet.

16:225-228.

1970b. Selection for the length of the spermatozoanthe mouse. Genet. Res., Camb. 16:261-275.

Woolley, D. M. 1970c. The midpiece of the mouse spermatozoon: Its

form and development as seen by surface replication. J. Cell

Sci. 6:865-879.

11

Woolley, D. M. and R. A. Beatty. 1967. Inheritance of midpiecelength in mouse spermatozoa. Nature, Lond. 215:94-95.

Yasuzumi, G. 1956. Spermatogenesis in animals as revealed byelectron-microscopy. I. Formation and sub-microscopicstructure of the middle-piece of the albino rat. J.

biophys. biochem. Cytol. 2:445-450.

Zamboni, L., R. S. Thompson and D. Moore-Smith. 1972. Fine mor-phology of human oocyte maturation in vitro. Biol. Reprod.7:425-457.

12

CHARACTERISTICS OF SPERMATOZOAN MIDPIECE LENGTH AND ITS

RELATIONSHIP WITH ECONOMICALLY IMPORTANT TRAITS IN CATTLE' ,

S. D. Lukefahr and William Hohenboken

Department of Animal ScienceOregon State UniversityCorvallis, Oregon 97331

Received July 14, 1980

'Technical Paper No. 5569, Oregon Agricultural Experiment Station.Contribution to Western Regional Coordinating Committee WRCC-1,The Improvement of Beef Cattle through the Application of BreedingMethods.

13

Abstract

Statistical properties, inheritance of spermatozoan midpiece

length, and its association with bull reproductive traits and daughters'

dairy traits were examined in a population sample of 39 Holstein

bulls. Variation for midpiece length of individual cells was small

within bulls (coefficient of variation a 4.5%), but variation for

midpiece length did exist among bulls. Average midpiece length did

not differ in ampules in semen collected from the same ejaculate,

but differences did exist between ampules of semen collected from

the same bull at least 6 mo apart. Two methods of estimation yielded

heritabilities of midpiece length greater than one. Both were im-

precise, but both were consistent with the existence of additive

genetic variation for the trait. Moderate correlations between a

sire's midpiece length and his predicted difference for dairy produc-

tion traits were negative. Correlations between midpiece length

and semen quality and fertility were close to zero. Results suggest

that midpiece length is heritable and that it might be correlated

with economically important dairy production traits.

(Key words: Sperm midpiece length, cattle, production, reproduction.)

14

INTRODUCTION

Progeny testing can be used to estimate a sire's genetic merit

for lowly heritable traits and for female sex-limited traits such as

milk production. An alternate procedure would be to estimate breed-

ing value for the sex-limited trait from the sire's phenotypic merit

for another trait, provided the second were highly correlated geneti-

cally with the first and were highly heritable (24). In chickens,

such a parallel relationship may exist between packed sperm volume and

egg mass (9); and in mice and sheep, testes size and ovulation rate

are positively genetically correlated (7,8).

In mice, a positive relationship between spermatozoan midpiece

length and body weight at 13 to 17 wk of age has been reported (1).

Since the midpiece is composed of mitochondria surrounding the proxi-

mal region of the flagellum in an a-helical configuration, it is

possible that an increase in midpiece length associated with the

quantity of mitochondria could be associated with a higher rate of

oxidative phosphorylation (2). This in turn could be associated with

a variety of other important traits. Variation in midpiece length in

the mouse studies was attributable to a difference in mitochondrial

content (22). The number of mitochondria per spermatozoan of bull,

man, and mouse is approximately 10, 10, and 350 (4). Midpiece length

in mice is highly heritable (.76 ± .02; .97 ± .36) but is not corre-

lated with lowly heritable traits such as fertility (20,23,21). A

general lack of age and maternal effects for midpiece length has also

been reported (3,15).

15

Biologically, mitochondria are the energy transformers of the

cell. Many important enzymes that are involved directly in the Krebs

Cycle are synthesized according to mitochondrial DNA instructions

(18). Nuclear and mitochondrial DNA coded proteins may interact

throughout cell metabolism and growth (19). In Drosophila and maize,

a close correspondence between actual heterosis and mitochondrial

complementation has been demonstrated (11,16). More importantly,

controversial evidence of mitochondrial duplication, mitochondrial

recombination and division, and restoration of mitochondrial content

following union of the sperm and ova has been reported (17,25).

Our objectives were to describe statistical properties of

spermatozoan midpiece length (MPL) in Holstein bulls, to partition

variation in MPL among bulls, between separate collections within

bulls, and within collections, to examine the inheritance of MPL,

and to measure correlations between MPL and fertility and dairy pro-

duction traits.

EXPERIMENTAL PROCEDURES

To increase visibility of the midpiece region, thawed semen was

diluted 1:15 with physiological saline phosphate buffer solution,

fixed in osmium tetroxide (4% aqueous) for 10 min, stained for 1 h

in Harris' Alum Hematoxylin solution, counterstained in a 2.5% solu-

tion of ferric alum for 10 min, and differentiated in picric acid for

another 10 min, an adaptation of the method of Hancock (6). Under

light microscopy, spermatozoan MPL was measured with a rotometer.

16

To ensure that MPL was being measured consistently, in a pilot

trial three repeat measurements of MPL were made for each of 100

sperm cells from each of two Holstein bulls. Computation of sample

variance and repeatability of MPL (for each bull) allowed calculation

of the required number of cells to measure per bull (McClave and

Dietrich, 10, p. 228) and the required number of repeat measurements

per cell for accurate determination of a bull's average MPL.

A second pilot trial was conducted to ensure that variation for

average MPL was minimal between ampules from the same ejaculate

(variation due to micro-environmental influences). Twenty-five cells

were measured for MPL from each of two ampules from each of three

Holstein bulls. Data were analyzed by heirarchical analysis of var-

iance.

In the main experiment, 39 Holstein bulls were chosen at random

from the battery of American Breeders Service, DeForest, WI (with

stipulations that their repeatability for Predicted Difference for

milk exceeded .60 and that semen from each bull was available from

two collections at least 6 mo apart). Twenty-five cells were measured

for MPL per ampule per bull. These data were analyzed by hierarchical

analysis of variance to partition variation in MPL to differences

among bulls, differences between collection periods (at least 6 mo

apart) within bulls, and differences within ampules within bulls.

To study the inheritance of MPL, the symmetric differences squared

method of Grimes and Harvey (5) was used, with the assumption that

maternal effects of MPL were not important. For each of the 741

17

possible pairs of bulls ((39 x 38)/2), the squared difference for

average MPL was computed. The genetic relationship (R) between each

pair of bulls also was computed. Based upon the assumption that

the genetic relationship of the particular pair of bulls and upon

genetic variation for MPL in the population, the model

(MPL. - MPL.)2

= VE + (1-R) VA (1)

2

was solved by regression methods. IMPL. and MPL. are average midpiece

lenghts for pairs of bulls (i # j), VE is residual variation, VA is

additive genetic variation and R is genetic relationship between

the pair of bulls in question. In comparison to the standard linear

regression model:

Y = a + bX, (2)

half the squared difference for MPL corresponds to Y, 1-R corresponds

to X, a is an estimate of VE for MPL in the population of interest

and VA

corresponds to the regression coefficient b. Heritability

of MPL was estimated as the ratio of VA

to VA + VE. For comparison,

heritability also was estimated by paternal half-brother analysis.

The mathematical model included only sires of bulls and the residual

term as sources of variation. The standard error of heritability

was computed according to the approximation formula of Osborne and

Patterson (14). Finally, product-moment correlations were computed

between MPL and fertility and dairy production traits on which data

were available from American Breeders Service and official 1979 USDA

sire summaries, respectively.

18

RESULTS AND DISCUSSION

For three measurements of MPL for each of 100 cells from two

bulls, repeatabilities were .66 and .74. We therefore decided only

one measurement per sperm cell would be made in subsequent studies.

The decision to measure 25 cells per bull was based upon statistics

from this preliminary trial (Table 1).

Results in Table 2 indicate most importantly that differences

in average MPL between ampules collected from the same ejaculate

were small, accounting for only 2% of the variation. Our purpose

in conducting this trial was to ensure that micro-environmental factors

did not affect MPL significantly. Mukherjee and Singh (12) also

reported little difference in MPL between slides within collections

within three dairy breeds of bulls.

Average MPL for all bulls was 13.41 um with a standard deviation

of .43. Statistically significant differences did exist among the

39 bulls (Table 3). Mukherjee and Singh (12) also reported differences

among sires in average MPL, while Mukherjee and Singh (13) reported

significant among-breed differences as well. Differences in average

MPL between ampules of semen collected at least 6 mo apart were sig-

nificant, accounting for 14% of the phenotypic variation. However,

the correlation between a bull's average MPL in the two collections

exceeded .80. In the experiments of Mukherjee and Singh (12,13),

variation in MPL from seasonal and between-collection differences

was not significant.

Some 85% of paired combinations of individuals from the 39-bull

19

population sample were not related genetically. Relationships between

the remaining pairs ranged from 3.125 to 31.125%. In Table 4, the

average difference in MPL is shown for each genetic relationship.

Although the difference in MPL and R were not linearly related, there

was some tendency for the MPL difference to be smaller between related

than between unrelated pairs of bulls, as would be expected if MPL

were heritable.

By using the symmetric differences squared method (5), the follow-

ing linear model was obtained:

2

MPLJ

-.038 + (1-R).165, (3)

where -.038 and .165 are estimates of environmental and additive

genetic variance.

Heritability for MPL was:

h2

= -.0381

6+

5

.1651.30 ± 1.13 (4)

Heritability of MPL from paternal half-brother analysis, based

upon eight paternal half-brother families of two to five bulls each,

was 1.09 ± 1.03. Both the traditional method and the symmetric

differences squared method yielded imprecise estimates of heritability

because of limited data and for the latter method the preponderance

of unrelated pairs of bulls. Both estimates, however, are consistent

with the existence of additive genetic variation for the trait.

As shown in Table 5, daughter dairy traits were not highly corre-

lated with a sire's average MPL (based upon 25 cells from each of two

20

collections taken at least 6 mo apart). These correlations are neither

genetic nor phenotypic, in the commonly accepted sense, since they

relate MPL, measured directly on the bulls, to production traits

measured on variable numbers of daughters. Magnitude and sign of

the correlations would be a function of the genetic correlation be-

tween MPL and the dairy trait of interest as well as .50 (accounting

for the Mendelian segregation between sire and daughter), square

roots of heritabilities of MPL and dairy trait, and the number of

daughters. For the correlations which are negative, it can be in-

ferred that the genetic correlation, if real, must also be negative;

and sires with larger than average MPL would tend to produce daughters

below average for dairy production traits.

Correlation coefficients between MPL and semen quality and ferti-

lity traits were all near zero (Table 6). In addition, the correlation

between a sire's average MPL and the percentage of his daughters

culled during their first lactation was only .15 (Table 5). Thus,

there was no evidence of association between MPL and fitness traits.

The 39 Holstein bulls in our population sample all had highly

repeatable Predicted Differences for dairy traits, and all were in

use at a commercial artificial insemination organization. Thus,

they were a random sample of all Holstein bulls neither for dairy

nor for fertility traits. Whether they constituted a random sample

with respect to spermatozoan MPL is dependent upon the correlation,

in the original unselected population, between MPL and the traits

upon which selection of the bulls for extensive A.I. use was based.

21

Work currently is underway to investigate variation among bulls for

MPL and to compute heritabilities and genetic and phenotypic correla-

tions between MPL and economically important traits in two beef cattle

populations not subject to these limitations.

ACKNOWLEDGEMENT

This work was supported through the generous donation of Holstein

semen and the provision of data on fertility by American Breeders

Service, DeForest, WI 53532.

22

REFERENCES

1. Beatty, R. A. 1969. A genetic study of spermatozoan dimensionsin mice selected for body weight. Indian J. Hered. 1:1.

2. Beatty, R. A. 1971. The genetics of size and shape of sperma-tozoan organelles. In: Proc. Int. Symp. on The Geneticsof the Spermatozoon. Pages 97-115. Edinburgh.

3. Beatty, R. A., and D. P. Mukherjee. 1963. Spermatozoan charac-teristics in mice of different ages. J. Reprod. Fertil.6:261.

4. Fawcette, D. W. 1975. The mammalian spermatozoon. Develop. Biol.44:394.

5. Grimes, L. W., and W. R. Harvey. 1980. Estimation of geneticvariances and covariances using symmetric differencessquared. J. Anim. Sci. 50:634.

6. Hancock, J. L. 1952. The morphology of bull spermatozoa. J.

Exp. Biol. 29:445.

7. Islam, A.B.M.M., W. G. Hill, and R. B. Land. 1976. Ovulationrates of lines of mice selected for testis weight. Genet.Res., Camb. 27:23.

8. Land, R. B., and W. R. Carr. 1975. Testis growth and plasma LHconcentration following hemicastration and its relation withfemale prolificacy in sheep. J. Reprod. Fertil. 45:495.

9. Marks, H. L. 1978. Possible relationship between packed spermvolume and egg mass in domestic fowl. Sep. Exper. 34:443.

10. McClave, J. T., and F. H. Dietrich II. 1979. Statistics. DellenPublishing Company, San Francisco.

11. McDaniel, R. G., and B. G. Grimwood. 1971. Hybrid vigor in droso-phila: respiration and mitochondrial energy conservation.Comp. Biochem. Physiol. 38 B:309.

12. Mukherjee, D. P., and S. P. Singh. 1965. Breed differences incharacteristics of bull spermatozoa. Indian J. Vet. Sci.35:213.

13. Mukherjee, D. P., and S. P. Singh. 1966. Seasonal variations inthe characteristics of bull spermatozoa. Indian J. Vet. Sci.36:104.

23

14. Osborne, Robert, and W.S.B. Patterson. 1952. On the samplingvariance of heritability estimates derived from varianceanalysis. In: Proc. Royal Soc. Edinburgh. 64 B:456.

15. Pant, K. P. 1971. Patterns of inheritance in the midpiecelength of mouse spermatozoa. In: Proc. Int. Symp. on TheGenetics of the Spermatozoon. Pages 116-120. Edinburgh.

16. Sarkissian, I. V., and H. K. Srivastava. 1967. Mitochondrialpolymorphism in maize. II. Further evidence of correlationof mitochondrial complementation and heterosis. Genetics57:843.

17. Soupart, P., and P. A. Strong. 1974. Ultrastructural observa-tions on human oocytes fertilized in vitro. Fertil. Steril.

25:11.

18. Wagoner, R. P. 1972. The role of maternal effects in animalbreeding. II. Mitochondria and animal inheritance. J.

Anim. Sci. 35:1280.

19. Woodward, D. 0., D. L. Edwards, and R. B. Flavell. 1970. Nucleo-cytoplasmic interaction in the control of mitochondrial struc-ture and function in neurospora. Symp. Soc. Exp. Biol. 24:

55.

20. Woolley, D. M. 1970a. Selection for the length of the sperma-tozoan midpiece in the mouse. Genet. Res., Camb. 16:261.

21. Woolley, D. M.the quantityGenet. Res.,

22. Woolley, D. M.Its form andJourn. Cell.

1970b. A test of the functional significance ofof mitochondria in the spermatozoa of mice.Camb. 16:225.

1970c. The midpiece of the mouse spermatozoon:development as seen by surface replication.Sci. 6:865.

23. Woolley, D. M. and R. A. Beatty. 1967. Inheritance of midpiecelength in mouse spermatozoa. Nature, Lond. 215:94.

24. Young, S.S.Y., and H. N. Turner. 1965. Selection schemes forimproving both reproduction rate and clean wool weight inthe Australian Merino under field conditions. Aust. J. Agric.

Res. 16:863.

25. Zamboni, L., R. S. Thompson, and D. Moore-Smith. 1972. Fine

morphology of human oocyte maturation in vitro. Biol. Reprod.

7:425.

24

TABLE 1. Statistical properties of midpiece length based upon thefirst of three measurements per cell

Bull 1 Bull 2

Sample size 100 100

Mean (um) 13.30 13.63

Variance .41 .36

Coef. of variation 4.8% 4.4%

25

TABLE 2. Hierarchical analysis of variance for differencesamong bulls and between ampules for midpiece length

Source df MSVariancecomponent

Bulls 2 9.73** .188

Ampules/Bulls 3 .33 .007

Cells/Ampules/Bulls 144 .15 .146

**p < .01

26

TABLE 3. Hierarchical analysis of variance for differences amongbulls and between collections for midpiece length

Source df MSVariancecomponent

Bulls 38 6.16** .096

Collections/Bulls 39 1.35** .047

Cells/Collections/Bulls 1,872 .19 .186

**P < .01

21

TABLE 4. The association between genetic relationship and MPLdifference for all possible pairs of bulls

Genetic relationship (%) Number of pairsAverage difference

in MPL (um)

0 632 .41

3.13 5 .20

6.25 38 .28

12.50 34 .45

25.00 29 .31

28.13 - 31.13 3 .31

28

TABLE 5. Product-moment correlations between sire midpiece lengthand daughters' dairy traits

Trait r

Predicted difference for milk yield -.28

Predicted difference for butterfat percentage -.04

Predicted difference for butterfat yield -.30

Predicted difference for dollars -.38*

Percent of daughters culled during first lactation .15

*P < .05

29

TABLE 6. Product-moment correlations between sire midpiece lengthand semen quality and fertility traits

Trait r

Motility at time of collection -.02

Percent abnormal cells -.05

Post-thaw motility -.07

Monreturn rate .02

THE INHERITANCE OF SPERMATOZOAN MIDPIECE LENGTHAND ITS RELATIONSHIP WITH GROWTH ANDREPRODUCTIVE TRAITS IN HEREFORD CATTLE

S. D. Lukefahr, William Hohenboken and J. S. Brinks

SUMMARY

30

Semen samples were collected from 80 yearling Hereford and Polled

Hereford bulls, and the relationship between average spermatozoan mid-

piece length (MPL) and growth and reproductive traits was examined.

Variation within bulls for average MPL was small (c.v. = 2.5%). The

effect of age was negligible in influencing average MPL, but breed

effects were highly significant. Heritability of MPL estimated by

paternal half-sib analysis was 0.84 ± 0.58. Phenotypic correlations

between average MPL and several growth and reproductive traits were

low. The magnitude of the genetic correlations between average MPL

and growth and most reproductive traits were zero to moderate and

were accompanied with large standard errors. These results suggest

that MPL is highly heritable. Further investigation, however, in

more suitable beef cattle populations is needed to determine whether

MPL is correlated genetically with traits of economic importance.

INTRODUCTION

Indirect selection can be an effective method by which to alter

a trait of interest in a desired direction. This is especially true

when the indirect traits is highly heritable and is highly genetically

31

correlated with the trait of interest (Young and Turner, 1965).

In mice, a positive relationship between spermatozoan midpiece

length (MPL) and mature body weight has been reported (Beatty, 1969).

Beatty found that each 0.2 pm increase in MPL was accompanied by a

10 gram increase in body weight. He hypothesized that an increase in

mitochondrial content (synonymous with increased MPL) might be related

to a higher rate of oxidative phosphorylation and might thus affect

energy dependent traits. In mice, variation among males in sperm

MPL has been reported (Beatty, 1969; Pant, 1971). Woolley (1970c)

ascertained that differences among males for MPL were due to differences

in the number of mitochondria-containing spiral gyres surrounding

the periflagellar membrane of the midpiece. Each mitochondrion was

found to occupy 0.58 of one gyre. On the spermatozoan midpiece of

bull, man and mouse, approximately 10, 10 and 350 mitochondria are

found (Fawcette, 1975). Woolley and Beatty (1967) and Woolley (1970b)

reported estimates of heritability for MPL in mice of 0.97 ± .36

and 0.76 ± .02, respectively. In addition, the influences of age

and maternal effects on MPL were minimal (Beatty and Mukherjee, 1963;

Pant, 1971); and the relationship between MPL and conception rate

was small (Woolley, 1970a).

In the study reported herein, semen samples from 80 yearling

Hereford and Polled Hereford bulls completing post-weaning gain tests

at the San Juan Basin Experiment Station of Colorado State University

were collected, prepared for microscopic examination and measured

for MPL determination. Objectives of the study were: 1) to obtain

32

descriptive statistics for MPL and performance traits of bulls, 2) to

investigate the effects of age, breed, and sires within breeds on

average MPL and performance traits of the bulls, 3) to estimate the

heritability of MPL and growth and reproductive traits and 4) to

determine phenotypic and genetic correlations between average MPL

and growth and reproductive traits.

MATERIALS AND METHODS

At the San Juan Basin Research Center, Hesperus, Colorado, of

Colorado State University, 225 Hereford, Polled Hereford, Angus,

Red Angus, Simmental, Limousine, Charolais, Red Brangus, Salers and

Santa Gertrudis bulls were evaluated for post-weaning rate of gain

on a 140-day test to approximately one year of age. For the study

reported herein, data from 63 Hereford and 17 Polled Hereford bulls

were utilized. Fifty-three Hereford and 7 Polled Hereford bulls

were excluded because stained semen samples from them were not appro-

priate for sperm MPL determination.

Bulls were group fed in pens of five or six bulls each. In

most pens, all bulls were from the same ranch; and in many pens,

all bulls were paternal half-sibs. Therefore, sire effects in sub-

sequent analyses were confounded to a degree with ranch and/or pen

effects.

Traits examined were actual weaning weight, weaning weight ad-

justed for calf age and age of dam, initial weight on test, average

daily gain on test, actual weight at the termination of the 140 -

day test and age adjusted yearling weight.

33

Shortly following the end of the test period, scotal circum-

ference (Coulter and Foote, 1979), semen quality and a subsequent

determination of average MPL were recorded. Semen traits included

percentages of motility, abnormal heads, separated heads, abnormal

midpieces, normal cells, abnormal tails, proximal droplets, distal

droplets and dead cells.

Staining of sperm cells was necessary to improve the visibility

of the midpiece region. Seventy of the 80 bulls had semen samples

collected on April 15-17, 1980, and staining was accomplished using

an adaptation of the method of Hancock (1952). Semen was smeared

onto glass slides and allowed to air-dry. Slides were then fixed

for 10 minutes throgh immersion in an osmium textroxide (4% aqueous)

vapor bath, stained for 1 hour in Harris' Alum Hematoxylin solution

and counterstained for 10 minutes in a 21% ferric alum solution.

After rinsing in distilled water and air drying, slides were ready

for MPL determination under light microscopy. Seventy of 84 slides

prepared using this technique were appropriate for MPL determination.

Cells were measured for MPL with the use of a rotometer.

Semen was collected from the remaining bulls a few days later.

The staining procedure for these bulls involved smearing fresh semen

samples equally diluted in Hancock's solution (1 gm Eosin Y per 60 ml

of 10% aqueous Nigrosine) across glass slides. After they were allowed

to dry, slides were ready for determination of MPL under phase-contrast

microscopy with the use of a rotometer. Of 70 slides prepared using

this method, only 10 were appropriate for MPL determination. Poor

34

sperm concentration and cracking of the stain made most of the slides

unusable for MPL determination.

To quantify the degree of variability for MPL, 100 cells were

measured for each of two bulls sampled at random from within the

population. Based upon the descriptive statistics for MPL from this

preliminary work, the number of cells required to accurately estimate

average MPL for the remaining bulls was determined.

In preliminary data analysis, staining method and/or type of

microscopy was examined as a potential source of variation in average

MPL. Samples prepared using the Hancock staining solution and ex-

amined under phase microscopy had MPL's consistently shorter than

samples stained with the adapted method of Handock (1952) and examined

under light microscopy. Therefore, average MPL of individuals that

had been evaluated by Hancock staining/phase microscopy were adjusted

to the expected modified Hancock staining/light microscopy equivalent

by the multiplicative factor of 1.062.

Variation in average sperm MPL and in bull growth and semen

traits was analyzed using a mathematical model including fixed sources

of variation for age and breed and the random effect of sires nested

within breeds. Analyses of variance utilized Harvey's LSML76 program.

Estimates of heritabilities, genetic correlations and phenotypic

correlations also were obtained from the analyses.

35

RESULTS AND DISCUSSION

From the preliminary examination of 100 cells from each of two

randomly chosen bulls, coefficients of variation were each 3.0%,

and the two bulls differed by 4.0% for average MPL. It was decided

that the measurement of 25 cells per bull was sufficient for an ac-

curate estimate of average MPL. The average within bull coefficient

of variation for all bulls in our study was 3.5%.

Least-squares means and residual standard deviations for average

MPL and for the growth and reproductive traits are presented in Table

1, with a summary of the analyses of variance results and estimated

heritabilities of the traits.

Only the effect of breeds was significant in influencing average

MPL. Least-squares means for average MPL for Herefords and Polled

Herefords were 13.04 pm and 13.35 pm, respectively. Mukherjee and

Singh (1966) detected significant variation among Indian dairy breeds

for MPL. Although the effect of sires within breeds on MPL was not

significant in this study, it accounted for a considerable proportion

of observed variance, as evidenced by the high heritability of the

trait. Significant variation among sires within dairy breeds was

reported by Mukherjee and Singh (1965) and Lukefahr and Hohenboken

(1981).

Age, breed and sires within breeds significantly affected several

growth and reproductive traits. As expected, age affected actual

weaning, initial and 140-day weights, but age did not affect repro-

ductive trait performance. The breed effect was significant for all

36

growth traits except actual and adjusted weaning weights and average

daily gain, with Herefords exceeding Polled Herefords. For some

reproductive traits, breed differences were important. Herefords

exceeded Polled Herefords for scrotal circumference and for percent-

ages of abnormal midpieces and proximal droplets but not for percent

abnormal heads.

Heritability of average MPL was estimated to be 0.84 ± 0.58.

Lukefahr and Hohenboken (1981) reported heritability estimates for

average MPL of Holstein bulls of 1.09 ± 1.03 and 1.30 ± 1.13. Her-

itability estimates for actual weaning weight, adjusted weaning weight

and initial weight were unreasonably high. It is likely that the

paternal half-sib correlations for those traits were biased by ranch

effects; the 36 sire groups contributing to the analysis came from

23 separate ranches. Ranch effects could include the overall mani-

festation of differences in herd health, maternal productivity, nutri-

tional program, climatic conditions and other effects. For 140 -

day weight and adjusted yearling weights, heritability estimates

were nearly as high, which could have reflected a carryover of ranch

effects or effects from paternal half-sibs being penned together.

The heritability for average daily gain was higher (0.89 ± 0.58)

than average values from the literature (Woldehawariat et al., 1977),

perhaps due to the partial confounding of ranch and/or pen effects

with sire groups.

The heritability estimate for scrotal circumference was 1.39

± 0.54. Coulter and Foote (1979) reported a mean heritability of

37

0.67 ± 0.10, averaged over age of bull for the same trait. In our

study scrotal circumference was not highly correlated phenotypically

with growth traits, such as 140-day weight (0.31). Therefore, the

high heritability was not likely a carryover effect of ranch and/or

pen effects on body size, but ranch/pen effects could have influenced

scrotal circumference directly. Estimates of heritability for semen

traits ranged from low to high in magnitude and all were accompanied

by large standard errors.

Phenotypic correlations between average MPL and growth and re-

productive traits were low (Table 2). This is in agreement with

results of Lukefahr and Hohenboken (1981), who reported that pheno-

typic correlations between MPL and semen and/or fertility traits

in Holstein bulls were close to zero. Although low, significant

correlations between average MPL and percentages of motility and

normal cells were observed. Lukefahr and Hohenboken (1981) reported

that average MPL of Holstein bulls was moderately negatively corre-

lated with predicted differences of their daughters for dairy traits.

Due to the small number of bulls (2.1) per half-sib family,

genetic correlations between avarage MPL and growth and reproductive

traits were all associated with large standard errors (Table 2).

Determination of whether econmically important beef production traits

are genetically correlated with average MPL will therefore have to

await further investigations. Such research involving other beef

cattle populations is currently underway.

38

LITERATURE CITED

Beatty, R. A. 1969. A genetic study of spermatozoan dimensions inmice selected for body weight. Indian J. Hered. 1:1-13.

Beatty, R. A. and D. P. Mukherjee. 1963. Spermatozoan characteris-tics in mice of different ages. J. Reprod. Fertil. 6:261-168.

Coulter, G. H. and R. H. Foote. 1979. Bovine testicular measure-ments as indicators of reproductive performance and their re-lationship to productive traits in cattle: A review. Therio-genology 11:297-311.

Fawcette, D. W. 1975. The mammalian spermatozoon. Develop. Biol.

44:394-436.

Hancock, J. L. 1952. The morphology of bull spermatozoa. J. Exp.

Biol. 29:445-453.

Lukefahr, S. D. and W. D. Hohenboken. 1981. Characteristics ofspermatozoan midpiece length and its relationship witheconomically important traits in cattle. J. Dairy Sci.(Accepted).

Mukherjee, D. P. and S. P. Singh. 1965. Breed differences in charac-teristics of bull spermatozoa. Indian J. Vet. Sci. 35:213-220.

Mukherjee, D. P. and S. P. Singh. 1966. Seasonal variations in thecharacteristics of bull spermatozoa. Indian J. Vet. Sci. 36:

104-108.

Pant, K. P. 1971. Patterns of inheritance in the midpiece length ofmouse spermatozoa. In: Proc. Int. Symp. on The Genetics of theSpermatozoon (p. 116-120). Edinburgh.

Woldenhawariat, Girma, M. A. Talamantes, R. R. Petty, Jr., and T. C.Cartwright. 1977. A summary of genetic and enviornmentalstatistics for growth and conformation characters of beefcattle. Dept. of Anim. Sci. Tech. Report 103. The TexasAgric. Exp. Sta., College Station.

Woolley, D. M. and R. A. Beatty. 1967. Inheritance of midpiece

length in mouse spermatozoa. Nature, Lond. 215:94-95.

Woolley, D. M. 1970a. A test of the functional significance of thequantity of mitochondria in the spermatozoa of mice. Genet.

Res., Camb. 16:225-228.

39

Woolley, D. M. 1970b. Selection for the length of the spermatozoanmidpiece in the mouse. Genet. Res., Camb. 16:261-275.

Wooley, D. M. 1970c. The midpiece of the mouse spermatozoon: Its

form and development as seen by surface replication. J. Cell

Sci. 6:865-879.

Young, S.S.Y. and H. Newton-Turner. 1965. Selection schemes for im-proving both reproduction rates and clean wool weight in theAustralian Merino under field conditions. Aust. J. Ag. Res.16: 863-880.

TABLE 1. Least-Squares Means, Residual Standard Deviations, Effects of Age, Breed and Sires WithinBreeds and Heritabilities of Average MPL and Growth and Reproductive Traits.

Trait

ResidualLeast-Squares Standard

Mean Deviation Age Breed Sires/Breed h2a

Average MPL (pm)

Actual Weaning Weight (kg)

Adjusted Weaning Weight (kg)

Initial Weight on Test (kg)

140-day Weight (kg)

Average Daily Gain (kg)

Adjusted Yearling Weight (kg)

Scrotal Circumference (cm)

Motility (%)

Abnormal Heads (%)

Separated Heads (%)

Abnormal Midpieces (%)

Normal Cells (%)

Abnormal Tails (%)

Proximal Drouplets (%)

Distal Droplets (%)

Dead Cells (%)

13.19

234.4

237.1

258.0

430.7

1.23

405.8

32.9

54.5

4.92

8.01

6.03

71.4

5.19

2.23

1.80

0.44

0.27

19.1

20.8

19.1

28.7

0.28

27.4

1.83

10.9

2.97

5.73

4.60

11.7

6.17

3.28

2.87

0.74

***

***

IMP

***

***

**

***

***

***

*

********

*

*

*

*

* * *

0.84 ± 0.58

1.57 ± 0.52

1.90 t 0.48

1.78 ± 0.50

1.45 ± 0.54

0.89 ± 0.58

1.32 ± 0.55

1.39 ± 0.54

__b

0.68 ± 0.60

0.19 ± 0.61

0.73 t 0.60

1.38 ± 0.55

1.08 ± 0.58

0.24 ± 0.61

0.23 ± 0.61

2.11 ± 0.45

*P < 0.05

**P < 0.01

***P < 0.05

aEstimated by paternal half-sib analysis involving 36 families with an averagesub-class size of 2.1 bulls.

bA negative estimate of heritability for percentage motility was obtained. 8

TABLE 2. Phenotypic and Genetic Correlations Between Average MPL and Growth and Reproductive Traits.

Actual Weaning Weight 80 -0.17 0.37 ± 0.43 Scrotal Circumference 80 0.07 -0.39 ± 0.48

Adjusted Weaning Weight 80 -0.20 0.45 ± 0.41 Motility ( %) 79 0.29*a

Initial Weaning Weight 80 -0.17 0.33 ± 0.41 Abnormal Heads (%) 79 0.02 .0.45 ± 0.56

Average 140-day Weight 80 -0.09 0.15 ± 0.44 Separated Heads (%) 79 -0.16 1.52 ± 1.73

Average Daily Gain 80 0.04 -0.25 ± 0.55 Abnormal Midpieces (%) 79 -0.07 -0.05 ± 0.55

Adjusted Yearling Weight 80 -0.13 0.36 ± 0.47 Normal Cells (%) 79 0.24* 0.04 ± 0.41

Abnormal Tails (%) 79 -0.16 -0.13 ± 0.48

Proximal Droplets (%) 79 -0.19 -1.08 ± 2.07

Distal Droplets (%) 79 -0.08 -1.39 ± 2.44

Dead Cells (%) 79 0.20 -0.43 ± 0.37

* P < .05

arg was not computed due to a negative estimate of heritability for percentage motility

42

APPENDIX 1. Average MPL, variance of MPL, percent repeatability andpredicted differences for several milk production traitsfor each of 39 Holstein bulls.

Bull I.D.Number

AverageMPL

Varianceof MPL

Repeat-ability

(%)

Milk Fat Fat(lb.) (%) (lb.) Difference

2980 13.23 0.24 97 +977 -.13 +16 +78

3220 13.67 0.21 63 -094 +.10 +10 +07

2810 13.42 0.16 66 +124 +.07 +15 +27

2910 13.10 0.32 60 +595 -.06 +13 +52

2475 14.14 0.19 98 +294 +.04 +16 +38

2628 13.18 0.16 73 +940 -.21 +03 +59

2546 13.71 0.12 84 +240 -.05 +02 +17

2668 13.20 0.19 73 +755 +.02 +31 +84

2766 13.70 0.17 60 +561 -.04 +15 +52

2818 12.97 0.08 68 +796 -.10 +14 +65

2820 13.57 0.16 82 +675 -.08 +13 +57

2576 13.14 0.12 79 +596 -.09 +09 +47

2691 13.40 0.12 73 +1036 -.17 +12 +77

2554 13.71 0.16 88 +477 -.06 +09 +40

2728 13.67 0.15 74 +406 +.04 +21 +51

2465 13.73 0.15 98 +1564 -.31 +09 +104

2389 13.11 0.09 98 +735 -.04 +21 +70

2636 14.19 0.34 69 +868 -.18 +05 +58

2781 13.47 0.18 62 +437 +.03 +20 +51

1958 13.24 0.15 99 +757 -.24 -08 +35

2588 13.17 0.17 73 +647 +.05 +31 +78

1953 13.27 0.21 98 +236 +.24 +43 +69

2662 13.15 0.17 69 +789 +.05 +36 +93

2890 13.10 0.28 93 +488 +.03 +21 +53

3280 13.39 0.10 81 +761 -.21 -04 +40

2825 13.45 0.17 85 +1096 -.18 +13 +82

2831 12.65 0.14 74 +1034 -.10 +22 +89

43

APPENDIX 1. (Continued)

Repeat-Bull I.D. Average Variance ability Milk Fat Fat

Number MPL of MPL (%) (lb. (lb.)Difference

2845 13.19 0.10 73 +582 -.11 +05 +41

2758 12.92 0.28 73 +1780 -.03 +60 +182

2864 12.97 0.16 66 +1074 -.18 +12 +79

2807 14.20 0.26 67 +495 -.14 -03 +25

2685 13.16 0.32 96 +676 -.15 +03 +44

2665 13.43 0.12 70 +834 +.02 +33 +92

2798 13.26 0.13 63 +895 +.01 +34 +97

2913 13.31 0.25 91 +310 +.19 +38 +67

2744 13.72 0.22 72 +960 -.05 +27 +91

2680 13.75 0.27 63 +816 +.03 +34 +84

2875 13.42 0.13 74 +973 -.03 +31 +97

2885 13.83 0.17 78 +732 -.13 +07 +52